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Publication Date

2011

Document Type

Honors Project

Department

Biological Sciences

Keywords

Seeds-Dispersal, Ants-Behavior, Plants, Flowering of, Seed dispersal, Phylogenetics, Trait evolution, Bayesian, Correlated evolution, Comparative methods, Forest plants-Phenology, Herbaceous plants-Phenology, Temperate deciduous forest

Abstract

Myrmecochory, the dispersal of seed by ants, is an unusual seed dispersal mechanism that is seen commonly only in two biomes, the dry Mediterranean-type shrublands of the Southern Hemisphere and the mesic temperate deciduous forests of the Northern Hemisphere. Although several well-supported hypotheses have been advanced to explain the evolution of ant dispersal in the former biome, no generally accepted explanation exists for the high frequency of this trait in temperate deciduous forests. In this study, I present a new, cohesive hypothesis for the high frequency and repeated evolution of ant seed dispersal in the temperate deciduous forest biome. An association between seed dispersal by ants and early spring flowering has been noted previously, but has never examined in a phylogenetic context. Here I propose that forest plants that have evolved to take advantage of the highly profitable early spring temporal niche, when light, nutrients, and water availability are high in the forest understory, are constrained to short stature by the limited time available for growth to exploit this niche. Consequently, short stature of early spring flowering plants (e.g., "spring ephemerals") may have provided the ecological context for the evolution of ant seed dispersal , one of the few effective means of dispersal likely available to short-statured plants obscured by taller, summer-green plants emerging later in the growing season. I used a data set including 319 species of forest plants from temperate deciduous forest areas in eastern North America, Europe, and East Asia to test for correlated evolution among plant seed dispersal mode, flowering phenology, and height. Results show that ant seed dispersal, short plant height, and early spring flowering are significantly correlated, providing strong evidence to support this hypothesis.

Language

English

Comments

58 p. : ill. Honors Project-Smith College, Northampton, Mass., 2011. Includes bibliographical references (p. 43-58)

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